Voltage amplifying piezoelectric-transformers, (Rosen transformers), which are typically of a generally elongated rectangular solid shape and comprise piezoelectric material in which are present two regions of different polarization directions, are known. As viewed in front elevational cross-section, such a piezoelectric-transformer can be described as having, at one longitudinally disposed side thereof, a region of vertically oriented polarization direction material with driving voltage electrodes attached thereto at upper and lower surfaces thereof, one of which is considered to be a reference electrode. On an opposite longitudinally disposed side thereof there is present a region of horizontally oriented polarization direction material with an output electrode attached at the vertically oriented end thereof. In use a voltage applied across the driving voltage electrodes appears amplified at the output electrode, (with respect to the reference electrode).
Also known are generally elongated rectangular solid shaped Piezoelectric gyroscopes which serve to produce a voltage at sensing electrodes thereof which is proportional to an angular rotation velocity of said piezoelectric-gyroscope about a longitudinally oriented axis therethrough. The mechanism of operation involves Coriolis force mediated flexure in a direction which is perpendicular to both said longitudinal axis, and a direction of an applied driving voltage effected flex. As viewed in front elevational cross-section, such a piezoelectric gyroscope has, at one longitudinally disposed side thereof, two vertically stacked, (ie. one atop the other), regions of vertically oriented polarization direction material sandwiched between driving voltage electrodes attached thereto at upper and lower surfaces. One of said vertically stacked regions of vertically oriented polarization direction material has an upward polarization direction and the other a downward polarization direction. On an opposite longitudinally disposed side thereof, and as viewed in side elevation there are present two adjacent regions of horizontally oriented polarization direction material, (ie. one in front of the other as viewed in frontal elevation), sandwiched between sensing voltage electrodes attached thereto at front and back vertically oriented surfaces. One said adjacent region of horizontally oriented polarization direction material having, as viewed from atop thereof, a horizontal laterally to the right projecting polarization and the other said adjacent region of horizontally oriented polarization direction material having a horizontal laterally to the left oriented polarization direction. That is, the polarization plane and polarization directions on said second longitudinally disposed side are simply rotated ninety (90) degrees, (eg. horizontally oriented), from the plane of the polarization directions, (eg. vertically oriented), on said first laterally disposed side about said longitudinally oriented axis therethrough.
In use said Piezoelectric gyroscope is caused to rotate at an angular rotation velocity about said longitudinally oriented axis, which projects essentially centrally therethrough from said first longitudinally disposed side to said second longitudinally disposed side, and a flex effecting voltage is applied across the driving electrodes while an output voltage is sensed across said sensing electrodes. When both angular rotation velocity about said longitudinally oriented axis therethrough, and flex effecting voltage is present across the driving electrodes, it occurs that, (through the mechanism of Coriolis force), a voltage appears at the sensing electrodes which is related to said angular rotation velocity about said longitudinally oriented axis therethrough. Where the angular rotational velocity about said longitudinally oriented axis therethrough is at least an order of magnitude less than is the natural vibrational frequency of the piezoelectric gyroscope material, the output voltage at the sensing electrodes is typically directly proportional to said angular rotational velocity.
A problem with Piezoelectric gyroscope systems, however, is that the output voltage produced thereby is often of a magnitude which is less than optimum. To date no known system seeks to overcome said shortcoming by application of principals inherent in the operation of Piezoelectric-transformers.
It is also known that materials which are well suited for use in Piezoelectric-transformers and gyroscopes are ceramics in which can be effected regions of polarization direction by a "Polling procedure". Ceramics are inherently isotropic so that polarization can be determined by application of an electric field across the materials in excess of the coercive field thereof, (which is typically on the order of 1 MV/m), while raising the temperature of the material above the Curie point, and then cooling the material below this point to lock-in the induced domain structure. A reference which describes this procedure is titled "Smart Structures and Materials", Culshaw, Artech House, (1996).
A with an eye to the present invention a search of Patents was conducted, with the result being that very little was found, and nothing obviating of the present invention system was identified. Three Patents which describe angular or rotation measuring systems comprised of piezoelectric materials are:
U.S. Pat. No. 3,143,889 to Simmons et al., which provides for electrodes to be present on a piezoelectric material on top and bottom surfaces and on front and back surfaces.
U.S. Pat. No. 3,258,617 to Hart describes a piezoelectric system which positions sensing electrodes, (see (23) and (24) of FIG. 2 therein), at both the ends of a preferably rectangular shaped mass of piezoelectric material.
U.S. Pat. No. 3,141,100 to Hart describes a rather complex system comprised of a plurality of crystal quartz elements.
U.S. Pat. No. 3,736,446 to Berlincourt et al., describes a piezoelectric transformer with an electrode (17) at an end of a preferably rectangular shaped mass of piezoelectric material. This Patent also shows a system structure with various regions of polarization direction material present therein. Reference to FIG. 1 therein shows two regions (13) and (14) of oppositely directed vertical polarization at the leftmost side thereof as viewed in said FIG. 1, and with a region of horizontally polarized material at the right side (12) as so viewed.
U.S. Pat. No. 5,504,384 to Lee et al. shows another piezoelectric transformer with electrodes (11) and (12) at ends of an essentially rectangular shaped block of piezoelectric material. Also described are various regions of polarization present therein. Reference to FIG. 2 in said 384 Patent shows horizontally oppositely directed regions of piezoelectric material at laterally disposed ends of the essentially rectangular shaped block of piezoelectric material, with oppositely directed vertically polarized regions of piezoelectric material centrally located therewithin.
Articles which describe conventional Piezoelectric transformers and gyroscopes are:
A paper titled "Piezoelectric-Ceramic Cylinder Vibratory Gyroscope", by Hbe et al., Jpn. J. Appl. Phys., Vol. 31, (1992), describes a piezoelectric gyroscope with a cylindrical structure.
Another paper titled "Consideration On Equivalent Mechanical Circuits For Vibratory Gyroscope", by Kudo et al., IEEE Ultrasonics Symo., (1990) describes equations of gyro-motion and proposes many vibratory gyroscopes including one utilizing rotation motion in a double resonate vibrator system.
Another paper titled "Piezoelectric Vibratory Gyroscope Using Flexural Vibration Of A Triangular Bar", by Fujishima et al., IEEE Forth-Fifth Annual Symp. on Freq. Control, (1991), describes basic principals of a piezoelectric vibratory gyroscope and discloses development of a unique triangular bar flexural vibratory piezoelectric gyroscope.
A paper titled "Mathematical Theory Of The Fork-Type Wave Gyroscope", IEEE International Frequency Control Symposium, (1995) describes operation of Fork-type gyroscopes.
Another paper which describes Fork-type Vibratory Gyroscopes is titled "LiTaO.sub.3 Crystal Fork Vibratory Gyroscope" by Wakatsuki et al., IEEE Ultrasonics Symposium, (1994).
Additionally, a paper titled Finite Element Analysis Of Single Crystal Tuning Forks For Gyroscopes", by Kudo et al., IEEE Intl. Freq. Control Symp., (1996), describes the results of applying finite element analysis to tuning fork gyroscopes.
Even in view of the identified known prior art, there remains need for a piezoelectric gyroscope system which provides increased signal output by coupling the voltage amplification benefits of piezoelectric (Rosen) transformers to the angular velocity measuring capabilities of piezoelectric-gyroscopes.